Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge.

[Archit Taneja]

On 06/16/2017 08:13 PM, Eric Anholt wrote:
> Archit Taneja <architt@xxxxxxxxxxxxxx> writes:
>
> > On 06/16/2017 02:11 AM, Eric Anholt wrote:
> > > If the panel-bridge is being set up after the drm_mode_config_reset(),
> > > then the connector's state would never get initialized, and we'd
> > > dereference the NULL in the hotplug path.  We also need to register
> > > the connector, so that userspace can get at it.
> >
> > Shouldn't the KMS driver make sure the panel-bridge is set up before
> > drm_mode_config_reset? Is it the case when we're inserting the
> > panel-bridge driver as a module?
> >
> >
> > All the connectors that have been added are registered automatically
> > when drm_dev_register() is called by the KMS driver. Registering a
> > connector in the middle of setting up our driver is prone to race
> > conditions if the userspace decides to use them immediately.
>
> Yeah, this is fixing initializing panel_bridge at DSI host_attach time,
> which in the case of a panel module that creates the DSI device
> (adv7533-style, like you said I should use as a reference) will be after
> drm_mode_config_reset() and drm_dev_register().

Okay. In the case of the msm kms driver, we defer probe until the
adv7533 module is inserted, only then we proceed to drm_mode_config_reset()
and drm_dev_register(). I assumed this was the general practice followed by
most kms drivers. I.,e the kms driver defers probe until all connector
related modules are inserted, and only then proceed to create a drm device.

Feedback from others on this would be appreciated, though.

Thanks,
Archit

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